This invention relates to systems and methods for the detection of pathogens. More particularly, the invention relates to paper-based microfluidic systems for pathogen detection.
Antiretroviral therapy (ART) as a successful treatment to suppress human immunodeficiency virus (HIV), prolong life in HIV-infected patients, and reduce HIV infection transmission rates has become even more affordable and accessible in many developing countries. However, a majority of HIV-infected individuals do not receive ART (46% of HIV-infected patients by the end of 2011) due to lack of affordable, rapid, and sensitive HIV diagnostic tools at the point-of-care (POC).
CD4 cell count and clinical symptoms have been used to initiate and guide ART in developing countries. According to the WHO guidelines, ART is initiated when CD4+ cells fall below 350/μL with WHO Stage II or WHO clinical Stage III and IV irrespective of CD4 cell count. It has been reported that recommended clinical symptoms criteria might lead to false positive diagnosis when compared with virological criteria. CD4 cell counting strategy alone is not sufficient to monitor patients efficiently or detect early virological failure, which allow for accumulation of drug-resistant strains and reduce the efficacy of second-line ART regimens and consequently shortening the clinical durability of available ART in developing countries.
The early detection of virological failure allows for both targeted adherence interventions as well as better preservation of the efficacy of second-line regimens. Without virological failure confirmation, HIV health care providers may prescribe switching to premature second-line ART and more complex antiretroviral regimen. Virological suppression, however, represents a more accurate immunological response of the patient to ART. Therefore, for an improved accurate diagnosis of treatment failure and to expand access to ART, emerging technologies to facilitate viral load testing at the POC are urgently needed. POC viral load testing may lead to increasing the adherence and minimizing the drug resistance through timely detection of virological failure and converting of failing regimens.
Several technologies have been used to develop viral load methods such as ELISA (ExaVir™), reverse transcriptase polymerase chain reaction (RT-PCR) (Liat™ analyzer), ultrasensitive p24 assay, microfluidic nucleic acid amplification, miniaturized PCR, microfluidics and quantum dots, and nanoplasmonic detection on self-assembled gold nanoparticles. Although, these assays offer promising methods for viral load measurements, they are either in the development process, are relatively expensive, require air conditioning, and/or require skilled operators.
Therefore, current viral load technologies are not suitable for POC testing in resource-constrained settings. Thus, to increase access to ART, a rapid, inexpensive, and simple viral load test is urgently needed at the POC.